1. Field of the Invention
The invention relates to a power control unit that converts direct-current (DC) power to alternating-current (AC) power and supplying this converted power to an electric motor. More particularly, the invention relates to a structure for fixing a component part of a power control unit.
2. Description of Related Art
A power control unit that is mounted in a vehicle powered partially or entirely by electricity such as a hybrid vehicle or an electric vehicle or the like, and that converts DC power from an onboard DC power supply to AC power and supplying this converted power to an electric motor for driving the vehicle is known. The power control unit includes a step-up transformer that steps up the voltage of the DC power, and a power converter that converts the stepped-up DC power to AC power. Moreover, a power control unit provided with a step-down transformer that steps down the voltage of DC power is also known. The step-up transformer includes a reactor, a capacitor, and a switching element. The reactor and capacitor of the step-up transformer, the step-down transformer, and a power converter and the like are integrated by being fixed to a common structure such as a device case within which these are housed.
This device case is arranged in a space that houses a prime mover (i.e., a so-called “engine compartment”), and there are some cases in which a reactor, capacitor, and a bus bar that connects these together, and the like that are housed in the device case will vibrate from a road surface when the vehicle is being driven, or due to vibrations from an internal combustion engine. Also, a varying magnetic field may be created by a ripple current generated by a switch operation of a switching element of the power converter or the step-up transformer, and the reactor, capacitor, and bus bar and the like may vibrate from this varying magnetic field. This vibration may be transmitted to the device case and produce noise. Japanese Patent Application Publication No. 2006-94586 (JP 2006-94586 A) describes technology for preventing resonance among the reactor, the capacitor, and the bus bar by varying the directions in which they vibrate.
The reactor and the capacitor used in the step-up transformer, as well as the step-down transformer and the like of the unit are large or heavy, so they tend to resonate easily unless they are securely fixed. In order to securely fix these devices, it is possible to increase the number of locations where they are fixed to a structure such as a device case, and strengthen the structure, but doing so may lead to an increase in size of the unit, as well as an increased number of parts.